In part 2 I talked about how our wisdom needs to be open to reason. The main two ways that will happen is through personal study of scripture and the counsel of others. It's open to reason, meaning if the scriptures provide reason to believe our decision is unwise, we change it. It also means others can ask questions and provide reason as to why we may be faulty in our thinking. If your thinking is "God told me" that's not open to reason.
Another thing I now feel compelled to say about this is that seeking God's will should not happen on a merely case-by-case basis. Romans 12:2 says this:
"Do not be conformed to this world, but be transformed by the renewal of your mind, that by testing you may discern what is the will of God, what is good and acceptable and perfect."
This describes an ongoing process of the renewal of our minds, so that when the time comes to make a decision, we may discern God's will. That means we're consistently reshaping the way we think so that it accords with God's thoughts. We start to value what He values and hate what He hates, and then we engage in reasonable decision making with his priorities.
Alot more can be said about God's will. It's not my purpose to write the whole book on it. I merely wanted to show that the process involves wisdom, which is by its very nature a reasonable process. We are called to engage in a continual process of the renewal of our minds, pray for wisdom, and make a decision that applies God's general will as revealed in the scriptures to our specific situation. Sometimes that decision is not very clear (where to live) and sometimes it is (whether to steal). For the less clear decisions, there will be more searching of the scriptures, more praying, more seeking counsel, etc. But in either case, the process is the same as to what we are to do.
In the concluding part, I'll talk about how we should communicate this and what role the Holy Spirit has in "leading" or "speaking" in this process. I'll also briefly touch the Biblical examples of people receiving direct revelation of God's will (e.g. Abraham when commanded to sacrifice his son).